P. . Sirisakunwattanaporn, S. . Sermsuk, and E. . Chuntha, “Study of Problems and Needs of Teachers’ Instruction in Mathematics (Grade 3) in schools under Phitsanulok Primary Educational Service Area Office 3”, Humanities and Social Sciences Journal of Pibulsongkram Rajabhat University, vol. 14, no. 1, pp. 80–96, Aug. 2019.